BD allocation and IDMA driver question

Dan Malek dan at
Tue Aug 20 14:35:37 EST 2002

kas turi wrote:

>  I would like to know what is the difference between
> m8260_cpm_hostalloc and m8260_dp_alloc.

The 'hostalloc' allocates from a small pool of host memory.
This is usually used for small FIFOs as there is only a
page or so for use by the entire system.  The 'dp_alloc'
allocates from the CPM dual ported memory.

> .... The FCC driver
> uses the former API and the serial driver uses the
> latter API.

If you would read the comment in the FCC driver, you may
understand why :-)

> ..... When I try to use m8260_cpm_hostalloc to
> allocate buffer descriptor for the SPI driver the
> timesys 2.4 kernel hangs. When I use m8260_dp_alloc
> the SPI driver works.

The 'hostalloc' returns a kernel virtual address.  You
have to convert this to a physical address for the CPM DMA.

>   Has anybody developed a IDMA driver for 8260 for 2.4
> kernel?

There have been discussions about it on this mailing list.
You may wish to search the archives for more information.

	-- Dan

** Sent via the linuxppc-embedded mail list. See

More information about the Linuxppc-embedded mailing list